small iAVs in California

52 posts in this topic

So I did a first run-through (water through sand in soda bottle) and was a little surprised that sand hemorrhaged out through the holes the entire time. I expected some sort of stability to be reached but nope. I ended up with about 6 handfuls of sand in the collection bucket, plus the water was really discolored - I assume due to presence of silt.

It took about 25 seconds for the water to make its way to the bottom and start exiting the bottle and one gallon took about two minutes, maybe a little more. It's hard to tell what proportion of the water remained in the sand (I did mark one gallon on the collection bucket) due to the fact that the collection volume is now skewed by the sand that is mixed with water.

I'll do another pass to see if the cloudiness dissipates (hopefully).

In a little bit, I'll also post some pics of the location and will solicit design ideas from y'all.

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The second pass and more obviously the third were significantly clearer. Now in the collection bucket I can see through the water to the sand that has escaped. And by the 3rd pass it was only a few tablespoons worth.

The holes are 1/8" and all drilled on the front face at the bottom (where the wavy "nubbins" of the bottle are).

It took 10 minutes, though, for the whole gallon to empty out. Doesn't that kind of stand to reason, though? If I tried to pour in 10 gallons of water it would take longerâ€¦ and instead of using the 5 gallon bucket, I've got less sand (eyeball estimate, .5 to .75 gallon) so I have to wait to continue adding water because my container is topped up.

On all other fronts it looks like the sand is good but for the poor pore space size (say that 5x fast)â€¦ I'm wondering if I should dry out my sand and start anew just to be sure.

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Hi Gary, when you have a moment, I'd love to hear your opinion on my slow-to-drain sand (or possibly just small container of sand)...

Meanwhile, I'm back to mulling over how to set up my sandbeds so they're higher than my fishtank. Keep in mind that though we don't frequently have earthquakes, I should be cautious about height relative to weight and instability.

I think this post is mostly me thinking out loud - but feel free to shake me by the shoulders if I'm being stupid about something here.

Here's the spot I'm thinking of putting the system:

To the right is a square (93x93" or just shy of 8ft) slab of concrete that is 4" above grade - heavy duty, it seems to have held the previous owners' hot tub.

The grey boxy thing is the HVAC unit - so I'll need to maintain access to it for service

Behind the reed fencing are two IBCs connected to the downspout - eventual rainwater collection. One is currently 3/4 full from the last of the season's rains. I may fill them up with tap water to use as emergency water supply.

And there's a grassy area (with brick stepping stones).

I have a large tree - this makes digging and sinking the fishtank impossible. It also gives me a lot of shade. I don't see this as a negative - we have an overabundance of solar radiation (plants eventually shut down) and I'm happy to grow herbs and shade tolerant plants in this iAVs. There's dappled light at different times of day.

My thought is: Put the entire system on the concrete pad or, if I use 3 sections of IBC as growbeds, then they are on the pad while the fishtank can be on a cleared and level section of grass. This keeps the cement in front of the rainbarrels and the HVAC unit clear as well as the steps from the deck near the concrete pad.

I like the proximity to the rain barrels (useful for topping up the fishtank and as emergency backup water for the system (?)), but there's also a spigot nearby so it's not really an issue. I like the proximity to the house (easy to see when there's a problem), I like that I could turn what's a kind of eyesore into a productive grow area. Also, it would make it nice for my dad to sit outside on the deck off from his bedroom door when the plants are established.

So - given that I'm aware and accepting of the location's shortcomings (shade and all above ground), the thing I need to do is figure out how to raise 1/3-deep IBC sections high enough to be above a 2/3-deep section that is the fish tank.

Maybe I just stack concrete blocks the way Gary has. I have many that don't need to be where they are in the yard. Easy peasy.

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Maybe I just stack concrete blocks the way Gary has. I have many that don't need to be where they are in the yard. Easy peasy.

Really? That simple?

All you have to do is support the weight and be able to make it level, so concrete blocks should work just fine, assuming you have enough of them. I don't have experience using the IBC totes, but you'll probably want blocks for the center as well as each corner. That concrete pad looks perfect for supporting the kind of weight you'll be supporting.

Perhaps I missed it in an earlier post, but are you planning on putting any kind of rain cover over the system?

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The second pass and more obviously the third were significantly clearer. Now in the collection bucket I can see through the water to the sand that has escaped. And by the 3rd pass it was only a few tablespoons worth.

The holes are 1/8" and all drilled on the front face at the bottom (where the wavy "nubbins" of the bottle are).

It took 10 minutes, though, for the whole gallon to empty out. Doesn't that kind of stand to reason, though? If I tried to pour in 10 gallons of water it would take longerâ€¦ and instead of using the 5 gallon bucket, I've got less sand (eyeball estimate, .5 to .75 gallon) so I have to wait to continue adding water because my container is topped up.

On all other fronts it looks like the sand is good but for the poor pore space size (say that 5x fast)â€¦ I'm wondering if I should dry out my sand and start anew just to be sure.

Your observation about the amount of time that it took to pour a gallon water through your sand reveals the difficulty that we have in communicating information on iAVs. The "gallon" is specific to the 5-gallon bucket we used in tests. I never meant to suggest that you would have to pour a gallon through a much smaller container - like a drink bottle.

The purpose of the hydraulic conductivity tests is to ensure that the sand drains effectively, so all you have to do (if using a 2 litre PET bottle) is filled it about 3/4 full of sand and then pour sufficient water (equal to the remaining 1/4) into the bottle to gauge how quickly the water moves through the sand and drains from the bottle. If the sand is draining faster than you can pour water into the bottle (or even close to that) there is clearly no issue from an hydraulic conductivity perspective.

If you've posted the results of your pore space volume test, I can't see it. What is it about the number that caused you to regard your test as a poor result?

To the right is a square (93x93" or just shy of 8ft) slab of concrete that is 4" above grade - heavy duty, it seems to have held the previous owners' hot tub.

The grey boxy thing is the HVAC unit - so I'll need to maintain access to it for service

Behind the reed fencing are two IBCs connected to the downspout - eventual rainwater collection. One is currently 3/4 full from the last of the season's rains. I may fill them up with tap water to use as emergency water supply.

And there's a grassy area (with brick stepping stones).

I have a large tree - this makes digging and sinking the fishtank impossible. It also gives me a lot of shade. I don't see this as a negative - we have an overabundance of solar radiation (plants eventually shut down) and I'm happy to grow herbs and shade tolerant plants in this iAVs. There's dappled light at different times of day.

My thought is: Put the entire system on the concrete pad or, if I use 3 sections of IBC as growbeds, then they are on the pad while the fishtank can be on a cleared and level section of grass. This keeps the cement in front of the rainbarrels and the HVAC unit clear as well as the steps from the deck near the concrete pad.

I like the proximity to the rain barrels (useful for topping up the fishtank and as emergency backup water for the system (?)), but there's also a spigot nearby so it's not really an issue. I like the proximity to the house (easy to see when there's a problem), I like that I could turn what's a kind of eyesore into a productive grow area. Also, it would make it nice for my dad to sit outside on the deck off from his bedroom door when the plants are established.

So - given that I'm aware and accepting of the location's shortcomings (shade and all above ground), the thing I need to do is figure out how to raise 1/3-deep IBC sections high enough to be above a 2/3-deep section that is the fish tank.

Maybe I just stack concrete blocks the way Gary has. I have many that don't need to be where they are in the yard. Easy peasy.

Really? That simple?

The concrete pad is perfect. You should be able to place four sections of IBC (three for sand beds and one for a fish tank) directly on the concrete. If that's too tight....go with your plan to put the fish tank on the grassed area.

You will need a sump tank. Now, putting that below ground will be much less of an issue than having to sink the fish tank.....because the sump tank will be a much smaller container. The size of your sump tank will be driven by things like your pour space volume.....which is why we get you to take that measurement. Anyway, we can work that out later.

Since your concrete pad is 4" deep.....and your IBC sections are also elevated about another 5"- 6"....your excavation will not be very deep at all.....and you won't need to elevate the whole thing on cement blocks which simplifies things enormously.

If you contact tree roots during the excavation for the sump tank....either move the hole over a bit - if they are major roots - or - if the roots are small ones - cut through them.

The dappled light sounds good.....particularly during a California summer.

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Don't be concerned. I have infinite patience with people who are genuinely committed to learn.....and none at all with smart arses, naysayers and serial nutters. I think of you as being part of the former rather than the latter.

The central message in the Bucket Tests is that, to enjoy optimum success with iAVs, you should learn about the medium.

A combination of the pore space volume measurement and the hydraulic conductivity test will give you everything you need to know about the ability of a given sand sample to drain effectively. Measuring the pore space volume (and the water retention) will also help you determine how much water will be in play at any given time.....useful for calculating the size of your sump tank for example.

To the extent that you don't understand something, please continue to seek clarification.

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"To the extent that you don't understand something, please continue to seek clarification."

I will. And thank you.

And I appreciate your input on my site as well.

I had been aiming for as simple a setup as possible (ie circulation between only a fish tank and the grow beds) but truly adding a sump only minimally complicates it.

In the next few days I'll re-work my sand test with an eye toward timing a decreased amount of water as well as measuring the pore space volume - results won't be too skewed from having rinsed away whatever was clouding it up, right? I have a little "virgin" sand left (possibly even enough) or I could go beg some more from the vendor...

Then it's probably time to borrow my uncle's dremel to start deconstructing the IBCs.

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I had been aiming for as simple a setup as possible (ie circulation between only a fish tank and the grow beds) but truly adding a sump only minimally complicates it.

The upside of using a sump tank in your situation is that your growbeds can be placed on the ground which avoids the need for the support structure that would otherwise be necessary......and it's more practicable for vine crops like tomatoes, cucumbers and the like.....which are difficult to work with when the grow beds start of at waist height.

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I've been following. This thread with interest. As for your 2 liter bottle "bucket" test. If adding 1 gallon to a 5 gallon bucket which is 1/5 total volume' then maybe using 400 ml is the right amount for a 2 liter container. Just so you know, your "mistakes are really good learning opportunities, not only for you, but the rest of us as well. Please keep up the good work.

the three columns very angular, angular and sub angular are all sharp sand.

very angular is so sharp it will draw blood or wear your fingerprints away.

angular is what I use for potting mix if I can get it.

Look at the two middle columns,

sub angular is used for concrete, it needs to flow when it is poured and worked but only a little bit

sub rounded is for mortar, it is more plastic, it can be shaped with a trowel.

playground sand, landscaping sand, builders sand is most likely to be sub rounded.

it is also likely to be unwashed.

unwashed means means it could have some clay and dust in it.

the clay is a problem, the thing that makes clay what it is, is Al2O3 aluminium oxide. it forms crystals that contain water as part of its structure and that in turn attracts and holds more water (in the same way that soap does) and because clay is so fine it coats everything in a film of water.

notice I have used the word "likely" nothing is guaranteed in the world of retail, that's where your testing comes in.

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Struck out with another attempt to source sand - asked for "washed builders' sand" and sand with a high silica content, without carbonates... they didn't know what I wanted, doubted their "fine" or "coarse" sand was it. Their sand is sourced locally (so, sacramento valley, most likely making it crushed river rock).

I've got some nicely sliced IBCs waiting for sand... now if I could only find the right thing.

I may go back to more intensively looking at the playground sand (at least it didn't react with the vinegar, not sure if I can recreate the pore space test since I've already washed out whatever was clouding the water the first time around)

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Well, I've tried 4 places for ASTM-C33 Sand (aka Washed Builders' Sand, aka pure silica & no carbonates sand...) and nobody could help me. (ok, to be fair, I only asked for ASTM-C33 from 2 places, all four I asked for Washed Builders' Sand)...

I guess this is old news (2014), that there's such a thing as peak sand (2016), but am I experiencing that or am I just not trying hard enough?

In the end, I don't want to ship sand from god knows where, some massive number of miles just so I can grow "low impact" veggies.

If I am going to return to my playground sand option - that did well on the tests I did correctly and then fizzled when I fizzled, should I re-test the old sand I still have (that's essentially washed) to determine pore space volume & conductivity? Or should I request a new sample?

Make do with what I can find semi-locally? Or work harder to source the dang stuff from... somewhere...?

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truly they must - I've only looked in my county and the one to the left and well, google didn't pull anything up that clearly said **try this in Sac!!**. Thanks for pointing out the obvious and giving me more terminology. I've been trying the landscape supply place end of things.